1. Field of the Invention
The present invention relates to a wireless communication system and a method for transmitting a frame and a computer program product thereof, specifically to a wireless system and a method for transmitting a frame by dynamically changing the transmission mode and a computer program product thereof.
2. Descriptions of the Related Art
In recent years, while techniques of wired communication are developed slowly, those of wireless communication for portable mobile devices are developed rapidly due to the mass demand so it becomes the important developing field for the communication industry in the future. Wireless communication means to transmit data utilizing radio and the communication quality consequently is usually degraded by external interferences, which decrease transmission speed and reduce data rate. Therefore, how to increase the transmission speed and how to improve the data rate are the key issues in this field.
There exist many transmission modes for wireless communication systems, such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 16 quadrature amplitude modulation (16QAM), and 64 quadrature amplitude modulation (64QAM). Whether these transmission modes can be used relates greatly to the channel quality of a wireless communication system.
One category of the prior techniques for increasing transmission speed and data rate of a wireless communication system is to change transmission mode dynamically. The transmission mode is changed according to the carrier to interference plus noise power ratio (CINR) of the channel estimated by the terminal device. Different transmission modes need different levels of CINR. Changing transmission mode dynamically is to determine whether to adjust the transmission mode according to CINR values in order to achieve more stable and faster transmission speed.
The aforementioned method uses only the estimated CINR value to determine whether to change the transmission mode or not. Consequently, CINR estimator plays the key role here, i.e., the error affects the estimated value. If a higher channel quality of a wireless communication system is required, a better estimator is required as well, which increases the cost of a terminal apparatus. If a worse estimator is chosen, the efficiency of choosing transmission mode will be degraded. Consequently, how to increase the transmission speed and the data rate of a wireless communication system by dynamically changing transmission mode in a more efficient way and how to reduce the cost of terminal apparatus at the same time are the key issues.